Abstract

OBJECTIVES: To define factors affecting the stone-free rate of extracorporeal shockwave lithotripsy in the treatment of pediatric renal calculi, and to establish a regression model for pretreatment prediction of stone-free probability.

METHODS: From January 1999 through February 2012, 207 children with mean age 6.4 ± 3.8 years underwent shockwave lithotripsy with Dornier Lithotripter S for treatment of renal stones. The stone-free rate was evaluated 3 months after the last shockwave lithotripsy session with non-contrast computed tomography. Treatment success was defined as complete clearance of the stones with no residual fragments. Multivariate logistic regression analysis was used to identify independent risk factors and to predict the probability of being stone free.

RESULTS: The mean length of the stone was 11.6 ± 4 mm. The stone-free rate was 71%. Independent factors that adversely affect stone-free rate were increasing stone length and calyceal site of the stone. Relative risks for not being free of stones were 1.123 for stone length, 2.673 for stones in the upper or middle calyx and 4.208 for lower calyx stones.

CONCLUSION: Stone length and location are prognostic factors determining stone-free rate after shockwave lithotripsy for renal calculi in pediatric patients. Based on our analysis, shockwave lithotripsy should be recommended for renal pelvis stones up to 24 mm, upper or middle calyceal stones up to 15 mm and lower calyceal stones up to 11 mm.

Comments
1

This report shows the outcome of SWL in 57 children with stones in the kidney. It is slightly surprising that as many as 56% of the children required additional SWL sessions, a number that is higher than that in adults treated with wide indications. As expected the stone size and the stone density (HU) were the best predictors of treatment results. That SSD and BMI were without influence in a paediatric population is, however, expected. When children were treated for stones in the kidney with only analgesics and sedation there might be a risk that the treatment is suboptimal.

One important finding was that the stone clearance was the same irrespective of the stone location in the kidney. With a better estimate of the stone burden the information had been even more useful. The statement that a water cushion was used as coupling medium needs further explanation.

This report shows the outcome of SWL in 57 children with stones in the kidney. It is slightly surprising that as many as 56% of the children required additional SWL sessions, a number that is higher than that in adults treated with wide indications. As expected the stone size and the stone density (HU) were the best predictors of treatment results. That SSD and BMI were without influence in a paediatric population is, however, expected. When children were treated for stones in the kidney with only analgesics and sedation there might be a risk that the treatment is suboptimal.
One important finding was that the stone clearance was the same irrespective of the stone location in the kidney. With a better estimate of the stone burden the information had been even more useful. The statement that a water cushion was used as coupling medium needs further explanation.
Hans-Göran Tiselius